Illuminating apparatus



1. F; nuonm. AILLUMINATING APPARATUS.

APPLICATION FILED AUG-5| 19 18.

Patented J 11116 1, 1920.

2 SHEETS-SHEET 1- J. F. RHODIN.

ILLUMINATING APPARATUS.

APPLICATION FILED AUG-5| 1918.

1,341,674. Patented June 1,1920.

2 SHEETSSHEET 2- Jim's I R/MD/M continuous. strip or body of light such as UNITED STATES.

JACOB F. RHODIN, OF HIGHLAND PARK, MICHIGAN.

ILLUMINATING APPARATUS.

Specification of Letters Patent.

Application filed August 5, 1918. Serial No. 248,278.

To all whom it may concern:

Be it known that I, JAcoB F. Rr opm, a subject of the King of- Sweden, residmg at Highland Park, county of Wayne, State of Michigan, have invented a certaln new and useful Improvement in Illummatmg Apparatus, and declare the followmg to be a full, clear, and exact description of the same, such as will enable others skilled in the art to which it pertains to make and use the same, reference being had to the accompanying drawings, which form a part of th1s specification.

My invention relates to illuminating apparatus and an object of my improvements is to provide an apparatus wh ch shall throw a uniform stream of light in the direction required and avoid a glare that has been incident to the use of reflectors w1th single light-sources, at the same time providing for, in the first place greater concentration when needed, in the second place a milder and more even light than at present obtainable.

I secure this object in the device illustrated in the accompanying .drawlngs m which: I g

Figure 1 is a diagrammatic v1ew 11lustrating the construction and operation of an apparatus embodying my nvention.

Fig. 2 is a detail sectional v1ew of the reflector shown in Fig. 1 on enlarged scale to illustrate the details of construction ofreflectors with focusing rays and a lightdis ersing reflector for mild illumlnation. ig. 3 is a front elevation of an apparatus embodyin my invention, the construction of the re ector being somewhat IIlOdlfiBd.

Fig. 4 is a cross-section of the apparatus shown in Fig. 3.

Fig. 5 is a cross-section of an apparatus similar to Fig. Jr-showing apartlally obscuring screen.

As a general construction my inventlon contemplates using two sources of light spaced from each other w1th a symmetrical reflector between said lights symmetrically located with reference to the same. 'As a further application of my invention I contemplate a number of parts of such lights constituting together a circle or circles of lights with the reflector located wlthm the circle or circles, and such c1rc1e may be a would be made by a continuous incandescent filament or the like.

As a further extension of the application of my invention, when strong illumination and great efliciency are desired, I contemplate the extension of said reflector beyond the pair or pairs of sources of light, so that Patented June 1, 1920.

the light radiated outwardly shall be re- 7 flected as well as that radiated inwardly.

As a contributory means of obviating the glare, when mild illumination is desired and some degree of efliciency may be sacrificed, I interpose a screen to prevent the direct radiation from the source of light to the I field to be illuminated and this screen may be so adjusted or designed as to limit the degree of radiation to the required. extent. In the drawings A designates the reflector as a whole, I) and 6 indicate 0 positely located sources of light, prefera h grees apart, which. may be. oppositely 1o- -cated points of acircular lamp or light I).

In Fig. 1 the reflector A between the source of light 6 and 12 in the cross section of the apparatus is one thirdof a complete c1rc1e. A A are construction-lines showing the. continuation of the circle of which the section of the reflector is a part.

With this construction the distributing of the light on the reflector between the sources of light b and b will be uniform, because at a pointof said reflector near one of said sources of light the light will be stronger from the nearer sourceand will beproportionally weaker from the fartherv source. Upon any point of thecircleAsuch as A the effect of thelight upon an observer will *be uniform inasmuch as the same surface of said reflectorwill subtend, the same solid angle from any point on said circle. Of course, this will be approximately the truth in the region adjacent to the circle A My invention contemplates forming the surface ofthe reflector between the sources ly 120 deis taken consisting of a short extension of each of the rays beyond the point of intersection, and these two generatrixes as well as the two lights b and b are moved along some parallel directrixes such as coaxial circles (Fig. 2) or parallel straight lines (Fig. 6) the generatrixes will then form the constituent side surfaces f and f of the facets f. i

- With this construction in each generating plane, the angle between the rays striking one point on the circle, will be at all times 120 degrees. It will be noted that no light from the source b will be reflected by the surface 7, but all the light from source b will be reflected from the surface f of each of the facets. to point a on the circle, where the axis of the reflector intersects same. vAnd all the light from source?) will be similarly reflected and focused as well. It is evident from the construction that all the said facets are parts of two groups of ellipses, the foci of which are I) and b as radiating points template an elliptic curve circumscribing said triangle. The said curves approach the said circular are very closely within the said limit of 120 degrees center-angle, all possible ellipses through the three polnts of the triangle being confined between the circle and the parabola. The Parabolic construction is illustrated in Figs. 3 and 4, the elliptic construction in Figs. 5 and 6.

Referring to Figs. 3 and 4, a represents the reflector extending outward from the source of light 6., This is a surface formed by a part of a parabola having its focal point at a point 12 in the plane of the crosssection and at the opposite side of said light and being rotated around the axis 0 0.

Ifadially within the circular light or lamp I form a series of facets corresponding to the facets of Fig. 2, which in this case have their reflecting surfaces indicated by the reference character a and a to indicate that they are a continuation of the reflector a. In this case each ofthese reflecting surfaces is a small part of a parabola in cross section, the parabolas being indicated by d and having their foci at 6 The surfaces a of the facets f are formed by the revolution of these short sectionsof parabolas about the axis 0 c. The reflecting surfaces a are similarly formed by the revolution of parts of parabolas having their foci at 6 In Fig. 5 I have shown a screen e interposed to prevent the direct radiation of the lamp near the field of illumination. This screen permits of the light radiating to the reflecting surfaces a and a. The interior surface of screen 6 I intend to make lightreflecting in such a way as to secure the greatest possible radiation oflight to the visible reflectin surface a.

Returning to ig. 2 it is evident from the above given demonstration that the way the circular arc is illuminated from the acute corners of the inscribed 120 degrees of isosceles triangle makes it a most favorable distributer of light from these points, and if given a light dispersing surface such as that of dull silver, will form a luminous surface when so illuminated. For a circle, the oint of highest illumination is inA for an e lipse farther out in the direction of the axle, and

Egg-d a parabola the light expended will profromb to b at right angles to its direction. Under one of these-forms with the direct light rays screened from the front, I contemplate using this application for interior lighting when mild and even light is desired.

What'I- claim is:

1. In a head light, the combination of a circular light-source and a reflector consisting in a concave part outside the circle reflecting the light directly forward and a concave part inside the circle also reflecting the light directly forward, said light source being closely adjacent to the reflecting surface, the reflecting surface within said light source being continuous and free from obstruction. v

' 2. In a head light having an axis, a circular light source, said source having the center of its circle insaid axis and the plane thereof at right angles to the same, and a reflector which has a bowl-shaped surface formed by a generating curve revolved around said axis, said curve being made up of parts, which alternately face one point of the light source in the cross section at the same time being tangential to the diametrically opposite point, and alternately are tangential to the rst point and face the other.

3. In a head light having an axis, a circular light source, said source having the center of its circle in said axis and the plane thereof at right angles to the same, and a bowl-shaped reflector having one portion outside the light source which is an unbroken reflecting surface of rotation of a part of an conic section as generatrix, and one inner portion back of the plane of the light source created by the revolution of a plurality of parts of curves alternately facing and tangential to one point of the circle in the cross section.

parallel outward, evenly distributed 4. In a headlight having an axis, a light source disposed along a line around the said allel to said line, each of the intersectlons of said rings by planes through the axis alternately facing points of intersection of said line by said plane upon the opposite sides of said axis, said rings reflecting forward the li ht rays.

11 testim tion.

ony whereof, I sign this slaecifica- JACOB F. RHODIN. 

